Abstract
Single-polarization, single-photodiode-based direct-detection (DD) transceivers offer advantages for metro networks due to their simple and low-cost optical hardware structure. Single-sideband Nyquist-pulse-shaped subcarrier modulation (SSB Nyquist-SCM) is a promising signal format to achieve high information spectral density (ISD) in such DD systems. In this paper, we present theoretical and experimental evaluations of a variety of direct-detection SSB Nyquist-SCM system designs, operating at 100 Gb/s per wavelength in wavelength division multiplexing (WDM) metro network scenarios. Through simulations, several receiver-based digital linearization techniques to overcome the effect of signal-signal beat interference were investigated, and their performance compared with alternative approaches, including optical beat-interference cancellation receivers (BICRx) and coherent receivers (both heterodyne and homodyne). Subsequently, experimental assessments of the digitally-linearized DD receivers were carried out. Spectrally efficient (net ISD exceeding 3 b/s/Hz) 4 × 112 Gb/s WDM DD single-sideband 16-QAM Nyquist-SCM transmission over distances of up to 240 km (multi-span links) and 160 km (single-span links without mid-span amplification) were shown to be possible using uncompensated standard single-mode fiber.
Highlights
METRO networks are experiencing unprecedented traffic growth
To determine the minimum wavelength division multiplexing (WDM) channel spacing to achieve the highest possible information spectral density (ISD), initially, the channel spacing was varied from 33 to 50 GHz and the required optical signal-to-noise ratio (OSNR) at the hard decision forward error correction (HD-FEC) bit error ratio (BER) threshold of 3.8 × 10-3 was monitored without using signal-signal beat interference (SSBI) compensation (Fig. 8(a))
We reported theoretical and experimental assessments of single-polarization direct-detection (DD) transceiver designs, using digital and optical linearization techniques, for 100 Gb/s/λ spectrally-efficient WDM metro networking
Summary
METRO networks are experiencing unprecedented traffic growth. The provision of bandwidth-intensiveManuscript received XXX. High-performance computing, information and entertainment, supported by cloud services, broadband video and mobile technologies are creating a rapidly increasing demand for high capacity optical links. Wavelength division multiplexing (WDM) is commonly used in metro transport networks to provide significant capacity gains over single-channel systems, it is expected that, to cope with the ever-increasing traffic growth, higher data rates (100 Gb/s and above) per WDM channel will need to be deployed [2]. Due to the cost-sensitive nature of metro networks, it may be favorable to utilize single-polarization, single-photodetector direct-detection (DD) transceivers because of the lower complexity and cost of their optical hardware structures in comparison to polarization-multiplexing coherent transceivers [3, 4]. The performance of conventional DD SCM systems is severely degraded because of the nonlinear effect, introduced by the direct (square-law) detection in the receiver, referred to as signal-signal beat interference (SSBI). The signal-signal beating products fall within the signal bandwidth, and interfere with the wanted signal-carrier beating products
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